1. Field of the Invention
The present invention relates to devices and methods for securing soft tissue to bone, and more particularly, to suture anchors for proximating tissue to bone using knotless interference fixation.
2. Related Art
When soft tissue such as a ligament or a tendon becomes detached from a bone, surgery may be indicated to reattach or reconstruct the tissue. Various fixation devices, including sutures, screws, staples, wedges, and plugs have been used in the past to secure soft tissue to bone.
More recently, various types of suture anchors have been developed. The suture anchors are implanted in bone, and suture passed through the soft tissue is secured to the suture anchor. The technique usually requires the surgeon to tie knots in the suture, which is tedious and time-consuming, particularly in an arthroscopic procedure. Surgical procedures would be less cumbersome for the surgeon and ultimately more beneficial to the patient if the tissue could be attached to the bone without the surgeon having to tie suture knots.
U.S. Patent Publication No. 2002/0013608 A1, dated Jan. 31, 2002, of common assignment with the present application and incorporated herein by reference, discloses a method of graft fixation using an interference screw. Suture is attached to the graft and inserted into a pre-drilled hole. The interference screw is driven into the pre-drilled hole to secure the suture. The procedure would be simpler if the tissue could be transported toward the suture anchor more directly, and the step of inserting the suture into the pre-drilled hole could be eliminated. Enhancement of the pull-out strength of the construct also is desirable.
Insert molded suture anchors are disclosed in U.S. Pat. No. 5,964,783 issued on Oct. 12, 1999 to Grafton et al., of common assignment with this application and incorporated in its entirety herein by reference.
The present invention provides a suture anchor construct that does not require knots. The construct includes a ribbed or threaded suture anchor having a suture eyelet provided on a distal end of the anchor. Lengths of repair suture that have been passed through soft tissue are threaded through the eyelet and inserted simultaneously with the anchor into a preformed hole. Advantageously, a flexible eyelet can be formed in a polymeric suture anchor by insert-molding a looped length of suture within the suture anchor such that a closed portion of the suture loop extends from the distal end of the anchor.
The anchor of the present invention is used for tissue repair involving reattachment of soft tissue to bone. A hole for the suture anchor is preformed in bone. Installing the anchor and suture into the bone hole opposes the tissue to the bone. The suture is held in the preformed hole by an interference fit. The interference fit is established by a wedge effect on the suture between the suture anchor and the walls of the bone socket.
Pull out strength of the construct can be increased by various methods. The interference fit can be enhanced, for example, by forming twists in the limbs of at least a portion of the suture that passes alongside the installed suture anchor body within the preformed hole. Twisting the suture increases a cable friction effect (friction between the twisted lengths of suture) and also increases the wedge effect. The wedge effect similarly will be enhanced by forming knots in the suture, or utilizing suture formed with irregular thicknesses. See FIG. 4 of U.S. Pat. No. 5,964,783, for example.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.